Typical miniature gas sources generate gases at rates from about 0.05 to 100 cc/day and are used for a variety of purposes. A primary use of the gas source is to produce mechanical work, such as may be required for delivering fluids at low flow rates. Many miniature gas sources use chemical means to generate the gases; but these are often unreliable, resulting in time-dependent generation rates.
Another source for generating gases involves the use of an electrochemical means. Electrochemical means to generate gases generally are more accurate, reliable, albeit they require a power source, generally in the form of commercial batteries.
Types of gases generated electrochemically typically include hydrogen, oxygen, and carbon dioxide. In some instances, as described by Winsel in U.S. Pat. No. 5,242,565, the battery is the power source as well as being the hydrogen gas generator. Other examples of electrochemical oxygen generators have been described by Maget in U.S. Pat. No. 6,010,317. Their applications to fluid delivery have also been described by Maget in U.S. Pat. Nos. 4,687,423; 4,886,514; 4,902,278; 5,928,194; 5,938,640; 5,971,722; 6,383,165, and 6,413,238.
Additional examples of electrochemical generators releasing carbon dioxide and hydrogen have been described by Swanson, et. al., in U.S. Pat. No. 7,316,857 and by Maget in U.S. Pat. No. 6,780,304. Setting the gas generation rates of electrochemical generators, however, requires conventional current controllers.
For commercial commodity products, such as releasers of pheromones, fragrances, insecticides, etc., a low cost for the gas generator is of paramount importance. The purpose of the present invention is to describe miniature and autonomous oxygen-gas generators that are cost-compatible with commercial commodity products, and in some instances are low cost gas sources that do not, but could, require electronic controls.